My understanding is that they have to keep chats based on an order, *as a result of their previous accidental deletion of potential evidence in the case*[0].
And per their own terms they likely only delete messages "when they want to" given the big catch-alls. "What happens when you delete a chat? -> It is scheduled for permanent deletion from OpenAI's systems within 30 days, unless: It has already been de-identified and disassociated from your account"[1]